GUIDE
Why extension £ per m² is blunt
Last checked September 2026
Published 2026 guides often quote about £2,000–£3,400 per m² for a single-storey extension. This lab stores a compiled mid of £2,650 / m² for a rear single-storey, £2,800 / m² for a side return, £2,300 / m² for a two-storey (foundations shared) and £2,750 / m² for a wraparound — before spec, region, VAT and extras.
Glazing, kitchen fit-out, drainage and ground conditions move the figure more than the floor area. Use the size slider, then tick kitchen, bi-folds, steel, underfloor heat, planning and fees if they apply.
Regional factors are blunt. Inner London in this model is +30%. Get quotes.